Radar systems must be protected from the environment such as rain, snow, ice, etc., in some manner, usually by a structure called a radome. The design of a radome is not elementary. It must protect the transmit/receive (T/R) modules of the radar system for sensitivity compliance, it must allow transmission of RF energy through the radome, it must not reflect RF energy back at the radar system to prevent damaging its T/R modules, and the radome must be constructed at a suitable cost.
For inflated (air-supported) radomes made of a single-layer material such as Vectran, the optimum shape, from the perspective of reducing reflected energy back at the radar system, is a sphere. But, a sphere shaped radome must be extremely large and is thus costly. So, a prolate geometry is often used. But, the prolate geometry, especially when subject to wind loading and variations in air pressure, results in radar energy reflections which may damage the radar equipment housed within the radome.
In one example, an air-supported radome 103 feet tall had a base 103 feet in diameter, a top hemispherical region with a 60 foot radius, and a prolate region at the bottom. A radome reflected power of 8 dB above the transmit/receive module power was measured which damaged the transmit and receive modules of the radar system housed within the radome.
A rigid sandwich radome structure may not suffer from these reflections, but rigid sandwich radome structures are expensive, may have undesirable seams which can cause high scattering to degrade the radar performance, and are difficult to manufacture and erect when the size of the radome is, say, a hundred feet high with a radius of 60 feet.